xref: /petsc/src/ksp/pc/impls/gamg/util.c (revision 7453f77509fc006cbcc7de2dd772f60dc49feac5) !
1 /*
2  GAMG geometric-algebric multigrid PC - Mark Adams 2011
3  */
4 #include <petsc/private/matimpl.h>
5 #include <../src/ksp/pc/impls/gamg/gamg.h>           /*I "petscpc.h" I*/
6 
7 #undef __FUNCT__
8 #define __FUNCT__ "MatCollapseRow"
9 /*
10    Produces a set of block column indices of the matrix row, one for each block represented in the original row
11 
12    n - the number of block indices in cc[]
13    cc - the block indices (must be large enough to contain the indices)
14 */
15 PETSC_STATIC_INLINE PetscErrorCode MatCollapseRow(Mat Amat,PetscInt row,PetscInt bs,PetscInt *n,PetscInt *cc)
16 {
17   PetscInt       cnt = -1,nidx,j;
18   const PetscInt *idx;
19   PetscErrorCode ierr;
20 
21   PetscFunctionBegin;
22   ierr = MatGetRow(Amat,row,&nidx,&idx,NULL);CHKERRQ(ierr);
23   if (nidx) {
24     cnt = 0;
25     cc[cnt] = idx[0]/bs;
26     for (j=1; j<nidx; j++) {
27       if (cc[cnt] < idx[j]/bs) cc[++cnt] = idx[j]/bs;
28     }
29   }
30   ierr = MatRestoreRow(Amat,row,&nidx,&idx,NULL);CHKERRQ(ierr);
31   *n = cnt+1;
32   PetscFunctionReturn(0);
33 }
34 
35 #undef __FUNCT__
36 #define __FUNCT__ "MatCollapseRows"
37 /*
38     Produces a set of block column indices of the matrix block row, one for each block represented in the original set of rows
39 
40     ncollapsed - the number of block indices
41     collapsed - the block indices (must be large enough to contain the indices)
42 */
43 PETSC_STATIC_INLINE PetscErrorCode MatCollapseRows(Mat Amat,PetscInt start,PetscInt bs,PetscInt *w0,PetscInt *w1,PetscInt *w2,PetscInt *ncollapsed,PetscInt **collapsed)
44 {
45   PetscInt       i,nprev,*cprev = w0,ncur = 0,*ccur = w1,*merged = w2,*cprevtmp;
46   PetscErrorCode ierr;
47 
48   PetscFunctionBegin;
49   ierr = MatCollapseRow(Amat,start,bs,&nprev,cprev);CHKERRQ(ierr);
50   for (i=start+1; i<start+bs; i++) {
51     ierr  = MatCollapseRow(Amat,i,bs,&ncur,ccur);CHKERRQ(ierr);
52     ierr  = PetscMergeIntArray(nprev,cprev,ncur,ccur,&nprev,&merged);CHKERRQ(ierr);
53     cprevtmp = cprev; cprev = merged; merged = cprevtmp;
54   }
55   *ncollapsed = nprev;
56   if (collapsed) *collapsed  = cprev;
57   PetscFunctionReturn(0);
58 }
59 
60 
61 /* -------------------------------------------------------------------------- */
62 /*
63    PCGAMGCreateGraph - create simple scaled scalar graph from matrix
64 
65  Input Parameter:
66  . Amat - matrix
67  Output Parameter:
68  . a_Gmaat - eoutput scalar graph (symmetric?)
69  */
70 #undef __FUNCT__
71 #define __FUNCT__ "PCGAMGCreateGraph"
72 PetscErrorCode PCGAMGCreateGraph(Mat Amat, Mat *a_Gmat)
73 {
74   PetscErrorCode ierr;
75   PetscInt       Istart,Iend,Ii,jj,kk,ncols,nloc,NN,MM,bs;
76   MPI_Comm       comm;
77   Mat            Gmat;
78   MatType        mtype;
79 
80   PetscFunctionBegin;
81   ierr = PetscObjectGetComm((PetscObject)Amat,&comm);CHKERRQ(ierr);
82   ierr = MatGetOwnershipRange(Amat, &Istart, &Iend);CHKERRQ(ierr);
83   ierr = MatGetSize(Amat, &MM, &NN);CHKERRQ(ierr);
84   ierr = MatGetBlockSize(Amat, &bs);CHKERRQ(ierr);
85   nloc = (Iend-Istart)/bs;
86 
87 #if defined PETSC_GAMG_USE_LOG
88   ierr = PetscLogEventBegin(petsc_gamg_setup_events[GRAPH],0,0,0,0);CHKERRQ(ierr);
89 #endif
90 
91   if (bs > 1) {
92     const PetscScalar *vals;
93     const PetscInt    *idx;
94     PetscInt          *d_nnz, *o_nnz,*w0,*w1,*w2;
95     PetscBool         ismpiaij,isseqaij;
96 
97     /*
98        Determine the preallocation needed for the scalar matrix derived from the vector matrix.
99     */
100 
101     ierr = PetscObjectTypeCompare((PetscObject)Amat,MATSEQAIJ,&isseqaij);CHKERRQ(ierr);
102     ierr = PetscObjectTypeCompare((PetscObject)Amat,MATMPIAIJ,&ismpiaij);CHKERRQ(ierr);
103 
104     ierr = PetscMalloc2(nloc, &d_nnz,isseqaij ? 0 : nloc, &o_nnz);CHKERRQ(ierr);
105 
106     if (isseqaij) {
107       PetscInt       max_d_nnz;
108 
109       /*
110           Determine exact preallocation count for (sequential) scalar matrix
111       */
112       ierr = MatSeqAIJGetMaxRowNonzeros(Amat,&max_d_nnz);CHKERRQ(ierr);
113       max_d_nnz = PetscMin(nloc,bs*max_d_nnz);CHKERRQ(ierr);
114       ierr = PetscMalloc3(max_d_nnz, &w0,max_d_nnz, &w1,max_d_nnz, &w2);CHKERRQ(ierr);
115       for (Ii = 0, jj = 0; Ii < Iend; Ii += bs, jj++) {
116         ierr = MatCollapseRows(Amat,Ii,bs,w0,w1,w2,&d_nnz[jj],NULL);CHKERRQ(ierr);
117       }
118       ierr = PetscFree3(w0,w1,w2);CHKERRQ(ierr);
119 
120     } else if (ismpiaij) {
121       Mat            Daij,Oaij;
122       const PetscInt *garray;
123       PetscInt       max_d_nnz;
124 
125       ierr = MatMPIAIJGetSeqAIJ(Amat,&Daij,&Oaij,&garray);CHKERRQ(ierr);
126 
127       /*
128           Determine exact preallocation count for diagonal block portion of scalar matrix
129       */
130       ierr = MatSeqAIJGetMaxRowNonzeros(Daij,&max_d_nnz);CHKERRQ(ierr);
131       max_d_nnz = PetscMin(nloc,bs*max_d_nnz);CHKERRQ(ierr);
132       ierr = PetscMalloc3(max_d_nnz, &w0,max_d_nnz, &w1,max_d_nnz, &w2);CHKERRQ(ierr);
133       for (Ii = 0, jj = 0; Ii < Iend - Istart; Ii += bs, jj++) {
134         ierr = MatCollapseRows(Daij,Ii,bs,w0,w1,w2,&d_nnz[jj],NULL);CHKERRQ(ierr);
135       }
136       ierr = PetscFree3(w0,w1,w2);CHKERRQ(ierr);
137 
138       /*
139          Over estimate (usually grossly over), preallocation count for off-diagonal portion of scalar matrix
140       */
141       for (Ii = 0, jj = 0; Ii < Iend - Istart; Ii += bs, jj++) {
142         o_nnz[jj] = 0;
143         for (kk=0; kk<bs; kk++) { /* rows that get collapsed to a single row */
144           ierr = MatGetRow(Oaij,Ii+kk,&ncols,0,0);CHKERRQ(ierr);
145           o_nnz[jj] += ncols;
146           ierr = MatRestoreRow(Oaij,Ii+kk,&ncols,0,0);CHKERRQ(ierr);
147         }
148         if (o_nnz[jj] > (NN/bs-nloc)) o_nnz[jj] = NN/bs-nloc;
149       }
150 
151     } else {
152       SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_USER,"Require AIJ matrix type");
153     }
154 
155     /* get scalar copy (norms) of matrix */
156     ierr = MatGetType(Amat,&mtype);CHKERRQ(ierr);
157     ierr = MatCreate(comm, &Gmat);CHKERRQ(ierr);
158     ierr = MatSetSizes(Gmat,nloc,nloc,PETSC_DETERMINE,PETSC_DETERMINE);CHKERRQ(ierr);
159     ierr = MatSetBlockSizes(Gmat, 1, 1);CHKERRQ(ierr);
160     ierr = MatSetType(Gmat, mtype);CHKERRQ(ierr);
161     ierr = MatSeqAIJSetPreallocation(Gmat,0,d_nnz);CHKERRQ(ierr);
162     ierr = MatMPIAIJSetPreallocation(Gmat,0,d_nnz,0,o_nnz);CHKERRQ(ierr);
163     ierr = PetscFree2(d_nnz,o_nnz);CHKERRQ(ierr);
164 
165     for (Ii = Istart; Ii < Iend; Ii++) {
166       PetscInt dest_row = Ii/bs;
167       ierr = MatGetRow(Amat,Ii,&ncols,&idx,&vals);CHKERRQ(ierr);
168       for (jj=0; jj<ncols; jj++) {
169         PetscInt    dest_col = idx[jj]/bs;
170         PetscScalar sv       = PetscAbs(PetscRealPart(vals[jj]));
171         ierr = MatSetValues(Gmat,1,&dest_row,1,&dest_col,&sv,ADD_VALUES);CHKERRQ(ierr);
172       }
173       ierr = MatRestoreRow(Amat,Ii,&ncols,&idx,&vals);CHKERRQ(ierr);
174     }
175     ierr = MatAssemblyBegin(Gmat,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
176     ierr = MatAssemblyEnd(Gmat,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
177   } else {
178     /* just copy scalar matrix - abs() not taken here but scaled later */
179     ierr = MatDuplicate(Amat, MAT_COPY_VALUES, &Gmat);CHKERRQ(ierr);
180   }
181 
182 #if defined PETSC_GAMG_USE_LOG
183   ierr = PetscLogEventEnd(petsc_gamg_setup_events[GRAPH],0,0,0,0);CHKERRQ(ierr);
184 #endif
185 
186   *a_Gmat = Gmat;
187   PetscFunctionReturn(0);
188 }
189 
190 /* -------------------------------------------------------------------------- */
191 /*
192    PCGAMGFilterGraph - filter (remove zero and possibly small values from the) graph and symetrize if needed
193 
194  Input Parameter:
195  . vfilter - threshold paramter [0,1)
196  . symm - symetrize?
197  In/Output Parameter:
198  . a_Gmat - original graph
199  */
200 #undef __FUNCT__
201 #define __FUNCT__ "PCGAMGFilterGraph"
202 PetscErrorCode PCGAMGFilterGraph(Mat *a_Gmat,PetscReal vfilter,PetscBool symm)
203 {
204   PetscErrorCode    ierr;
205   PetscInt          Istart,Iend,Ii,jj,ncols,nnz0,nnz1, NN, MM, nloc;
206   PetscMPIInt       rank;
207   Mat               Gmat  = *a_Gmat, tGmat, matTrans;
208   MPI_Comm          comm;
209   const PetscScalar *vals;
210   const PetscInt    *idx;
211   PetscInt          *d_nnz, *o_nnz;
212   Vec               diag;
213   MatType           mtype;
214 
215   PetscFunctionBegin;
216 #if defined PETSC_GAMG_USE_LOG
217   ierr = PetscLogEventBegin(petsc_gamg_setup_events[GRAPH],0,0,0,0);CHKERRQ(ierr);
218 #endif
219   /* scale Gmat for all values between -1 and 1 */
220   ierr = MatCreateVecs(Gmat, &diag, 0);CHKERRQ(ierr);
221   ierr = MatGetDiagonal(Gmat, diag);CHKERRQ(ierr);
222   ierr = VecReciprocal(diag);CHKERRQ(ierr);
223   ierr = VecSqrtAbs(diag);CHKERRQ(ierr);
224   ierr = MatDiagonalScale(Gmat, diag, diag);CHKERRQ(ierr);
225   ierr = VecDestroy(&diag);CHKERRQ(ierr);
226 
227   if (vfilter < 0.0 && !symm) {
228     /* Just use the provided matrix as the graph but make all values positive */
229     MatInfo     info;
230     PetscScalar *avals;
231     PetscBool isaij,ismpiaij;
232     ierr = PetscObjectTypeCompare((PetscObject)Gmat,MATSEQAIJ,&isaij);CHKERRQ(ierr);
233     ierr = PetscObjectTypeCompare((PetscObject)Gmat,MATMPIAIJ,&ismpiaij);CHKERRQ(ierr);
234     if (!isaij && !ismpiaij) SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_USER,"Require (MPI)AIJ matrix type");
235     if (isaij) {
236       ierr = MatGetInfo(Gmat,MAT_LOCAL,&info);CHKERRQ(ierr);
237       ierr = MatSeqAIJGetArray(Gmat,&avals);CHKERRQ(ierr);
238       for (jj = 0; jj<info.nz_used; jj++) avals[jj] = PetscAbsScalar(avals[jj]);
239       ierr = MatSeqAIJRestoreArray(Gmat,&avals);CHKERRQ(ierr);
240     } else {
241       Mat_MPIAIJ  *aij = (Mat_MPIAIJ*)Gmat->data;
242       ierr = MatGetInfo(aij->A,MAT_LOCAL,&info);CHKERRQ(ierr);
243       ierr = MatSeqAIJGetArray(aij->A,&avals);CHKERRQ(ierr);
244       for (jj = 0; jj<info.nz_used; jj++) avals[jj] = PetscAbsScalar(avals[jj]);
245       ierr = MatSeqAIJRestoreArray(aij->A,&avals);CHKERRQ(ierr);
246       ierr = MatGetInfo(aij->B,MAT_LOCAL,&info);CHKERRQ(ierr);
247       ierr = MatSeqAIJGetArray(aij->B,&avals);CHKERRQ(ierr);
248       for (jj = 0; jj<info.nz_used; jj++) avals[jj] = PetscAbsScalar(avals[jj]);
249       ierr = MatSeqAIJRestoreArray(aij->B,&avals);CHKERRQ(ierr);
250     }
251 #if defined PETSC_GAMG_USE_LOG
252     ierr = PetscLogEventEnd(petsc_gamg_setup_events[GRAPH],0,0,0,0);CHKERRQ(ierr);
253 #endif
254     PetscFunctionReturn(0);
255   }
256 
257   ierr = PetscObjectGetComm((PetscObject)Gmat,&comm);CHKERRQ(ierr);
258   ierr = MPI_Comm_rank(comm,&rank);CHKERRQ(ierr);
259   ierr = MatGetOwnershipRange(Gmat, &Istart, &Iend);CHKERRQ(ierr);
260   nloc = Iend - Istart;
261   ierr = MatGetSize(Gmat, &MM, &NN);CHKERRQ(ierr);
262 
263   if (symm) {
264     ierr = MatTranspose(Gmat, MAT_INITIAL_MATRIX, &matTrans);CHKERRQ(ierr);
265   }
266 
267   /* Determine upper bound on nonzeros needed in new filtered matrix */
268   ierr = PetscMalloc2(nloc, &d_nnz,nloc, &o_nnz);CHKERRQ(ierr);
269   for (Ii = Istart, jj = 0; Ii < Iend; Ii++, jj++) {
270     ierr      = MatGetRow(Gmat,Ii,&ncols,NULL,NULL);CHKERRQ(ierr);
271     d_nnz[jj] = ncols;
272     o_nnz[jj] = ncols;
273     ierr      = MatRestoreRow(Gmat,Ii,&ncols,NULL,NULL);CHKERRQ(ierr);
274     if (symm) {
275       ierr       = MatGetRow(matTrans,Ii,&ncols,NULL,NULL);CHKERRQ(ierr);
276       d_nnz[jj] += ncols;
277       o_nnz[jj] += ncols;
278       ierr       = MatRestoreRow(matTrans,Ii,&ncols,NULL,NULL);CHKERRQ(ierr);
279     }
280     if (d_nnz[jj] > nloc) d_nnz[jj] = nloc;
281     if (o_nnz[jj] > (MM-nloc)) o_nnz[jj] = MM - nloc;
282   }
283   ierr = MatGetType(Gmat,&mtype);CHKERRQ(ierr);
284   ierr = MatCreate(comm, &tGmat);CHKERRQ(ierr);
285   ierr = MatSetSizes(tGmat,nloc,nloc,MM,MM);CHKERRQ(ierr);
286   ierr = MatSetBlockSizes(tGmat, 1, 1);CHKERRQ(ierr);
287   ierr = MatSetType(tGmat, mtype);CHKERRQ(ierr);
288   ierr = MatSeqAIJSetPreallocation(tGmat,0,d_nnz);CHKERRQ(ierr);
289   ierr = MatMPIAIJSetPreallocation(tGmat,0,d_nnz,0,o_nnz);CHKERRQ(ierr);
290   ierr = PetscFree2(d_nnz,o_nnz);CHKERRQ(ierr);
291   if (symm) {
292     ierr = MatDestroy(&matTrans);CHKERRQ(ierr);
293   } else {
294     /* all entries are generated locally so MatAssembly will be slightly faster for large process counts */
295     ierr = MatSetOption(tGmat,MAT_NO_OFF_PROC_ENTRIES,PETSC_TRUE);CHKERRQ(ierr);
296   }
297 
298   for (Ii = Istart, nnz0 = nnz1 = 0; Ii < Iend; Ii++) {
299     ierr = MatGetRow(Gmat,Ii,&ncols,&idx,&vals);CHKERRQ(ierr);
300     for (jj=0; jj<ncols; jj++,nnz0++) {
301       PetscScalar sv = PetscAbs(PetscRealPart(vals[jj]));
302       if (PetscRealPart(sv) > vfilter) {
303         nnz1++;
304         if (symm) {
305           sv  *= 0.5;
306           ierr = MatSetValues(tGmat,1,&Ii,1,&idx[jj],&sv,ADD_VALUES);CHKERRQ(ierr);
307           ierr = MatSetValues(tGmat,1,&idx[jj],1,&Ii,&sv,ADD_VALUES);CHKERRQ(ierr);
308         } else {
309           ierr = MatSetValues(tGmat,1,&Ii,1,&idx[jj],&sv,ADD_VALUES);CHKERRQ(ierr);
310         }
311       }
312     }
313     ierr = MatRestoreRow(Gmat,Ii,&ncols,&idx,&vals);CHKERRQ(ierr);
314   }
315   ierr = MatAssemblyBegin(tGmat,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
316   ierr = MatAssemblyEnd(tGmat,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
317 
318 #if defined PETSC_GAMG_USE_LOG
319   ierr = PetscLogEventEnd(petsc_gamg_setup_events[GRAPH],0,0,0,0);CHKERRQ(ierr);
320 #endif
321 
322 #if defined(PETSC_USE_INFO)
323   {
324     double t1 = (!nnz0) ? 1. : 100.*(double)nnz1/(double)nnz0, t2 = (!nloc) ? 1. : (double)nnz0/(double)nloc;
325     ierr = PetscInfo4(*a_Gmat,"\t %g%% nnz after filtering, with threshold %g, %g nnz ave. (N=%D)\n",t1,vfilter,t2,MM);CHKERRQ(ierr);
326   }
327 #endif
328   ierr    = MatDestroy(&Gmat);CHKERRQ(ierr);
329   *a_Gmat = tGmat;
330   PetscFunctionReturn(0);
331 }
332 
333 /* -------------------------------------------------------------------------- */
334 /*
335    PCGAMGGetDataWithGhosts - hacks into Mat MPIAIJ so this must have npe > 1
336 
337    Input Parameter:
338    . Gmat - MPIAIJ matrix for scattters
339    . data_sz - number of data terms per node (# cols in output)
340    . data_in[nloc*data_sz] - column oriented data
341    Output Parameter:
342    . a_stride - numbrt of rows of output
343    . a_data_out[stride*data_sz] - output data with ghosts
344 */
345 #undef __FUNCT__
346 #define __FUNCT__ "PCGAMGGetDataWithGhosts"
347 PetscErrorCode PCGAMGGetDataWithGhosts(Mat Gmat,PetscInt data_sz,PetscReal data_in[],PetscInt *a_stride,PetscReal **a_data_out)
348 {
349   PetscErrorCode ierr;
350   MPI_Comm       comm;
351   Vec            tmp_crds;
352   Mat_MPIAIJ     *mpimat = (Mat_MPIAIJ*)Gmat->data;
353   PetscInt       nnodes,num_ghosts,dir,kk,jj,my0,Iend,nloc;
354   PetscScalar    *data_arr;
355   PetscReal      *datas;
356   PetscBool      isMPIAIJ;
357 
358   PetscFunctionBegin;
359   ierr = PetscObjectGetComm((PetscObject)Gmat,&comm);CHKERRQ(ierr);
360   ierr      = PetscObjectTypeCompare((PetscObject)Gmat, MATMPIAIJ, &isMPIAIJ);CHKERRQ(ierr);
361   ierr      = MatGetOwnershipRange(Gmat, &my0, &Iend);CHKERRQ(ierr);
362   nloc      = Iend - my0;
363   ierr      = VecGetLocalSize(mpimat->lvec, &num_ghosts);CHKERRQ(ierr);
364   nnodes    = num_ghosts + nloc;
365   *a_stride = nnodes;
366   ierr      = MatCreateVecs(Gmat, &tmp_crds, 0);CHKERRQ(ierr);
367 
368   ierr = PetscMalloc1(data_sz*nnodes, &datas);CHKERRQ(ierr);
369   for (dir=0; dir<data_sz; dir++) {
370     /* set local, and global */
371     for (kk=0; kk<nloc; kk++) {
372       PetscInt    gid = my0 + kk;
373       PetscScalar crd = (PetscScalar)data_in[dir*nloc + kk]; /* col oriented */
374       datas[dir*nnodes + kk] = PetscRealPart(crd);
375 
376       ierr = VecSetValues(tmp_crds, 1, &gid, &crd, INSERT_VALUES);CHKERRQ(ierr);
377     }
378     ierr = VecAssemblyBegin(tmp_crds);CHKERRQ(ierr);
379     ierr = VecAssemblyEnd(tmp_crds);CHKERRQ(ierr);
380     /* get ghost datas */
381     ierr = VecScatterBegin(mpimat->Mvctx,tmp_crds,mpimat->lvec,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr);
382     ierr = VecScatterEnd(mpimat->Mvctx,tmp_crds,mpimat->lvec,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr);
383     ierr = VecGetArray(mpimat->lvec, &data_arr);CHKERRQ(ierr);
384     for (kk=nloc,jj=0;jj<num_ghosts;kk++,jj++) datas[dir*nnodes + kk] = PetscRealPart(data_arr[jj]);
385     ierr = VecRestoreArray(mpimat->lvec, &data_arr);CHKERRQ(ierr);
386   }
387   ierr        = VecDestroy(&tmp_crds);CHKERRQ(ierr);
388   *a_data_out = datas;
389   PetscFunctionReturn(0);
390 }
391 
392 
393 /*
394  *
395  *  PCGAMGHashTableCreate
396  */
397 
398 #undef __FUNCT__
399 #define __FUNCT__ "PCGAMGHashTableCreate"
400 PetscErrorCode PCGAMGHashTableCreate(PetscInt a_size, PCGAMGHashTable *a_tab)
401 {
402   PetscErrorCode ierr;
403   PetscInt       kk;
404 
405   PetscFunctionBegin;
406   a_tab->size = a_size;
407   ierr = PetscMalloc1(a_size, &a_tab->table);CHKERRQ(ierr);
408   ierr = PetscMalloc1(a_size, &a_tab->data);CHKERRQ(ierr);
409   for (kk=0; kk<a_size; kk++) a_tab->table[kk] = -1;
410   PetscFunctionReturn(0);
411 }
412 
413 #undef __FUNCT__
414 #define __FUNCT__ "PCGAMGHashTableDestroy"
415 PetscErrorCode PCGAMGHashTableDestroy(PCGAMGHashTable *a_tab)
416 {
417   PetscErrorCode ierr;
418 
419   PetscFunctionBegin;
420   ierr = PetscFree(a_tab->table);CHKERRQ(ierr);
421   ierr = PetscFree(a_tab->data);CHKERRQ(ierr);
422   PetscFunctionReturn(0);
423 }
424 
425 #undef __FUNCT__
426 #define __FUNCT__ "PCGAMGHashTableAdd"
427 PetscErrorCode PCGAMGHashTableAdd(PCGAMGHashTable *a_tab, PetscInt a_key, PetscInt a_data)
428 {
429   PetscInt kk,idx;
430 
431   PetscFunctionBegin;
432   if (a_key<0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_USER,"Negative key %d.",a_key);
433   for (kk = 0, idx = GAMG_HASH(a_key);
434        kk < a_tab->size;
435        kk++, idx = (idx==(a_tab->size-1)) ? 0 : idx + 1) {
436 
437     if (a_tab->table[idx] == a_key) {
438       /* exists */
439       a_tab->data[idx] = a_data;
440       break;
441     } else if (a_tab->table[idx] == -1) {
442       /* add */
443       a_tab->table[idx] = a_key;
444       a_tab->data[idx]  = a_data;
445       break;
446     }
447   }
448   if (kk==a_tab->size) {
449     /* this is not to efficient, waiting until completely full */
450     PetscInt       oldsize = a_tab->size, new_size = 2*a_tab->size + 5, *oldtable = a_tab->table, *olddata = a_tab->data;
451     PetscErrorCode ierr;
452 
453     a_tab->size = new_size;
454 
455     ierr = PetscMalloc1(a_tab->size, &a_tab->table);CHKERRQ(ierr);
456     ierr = PetscMalloc1(a_tab->size, &a_tab->data);CHKERRQ(ierr);
457 
458     for (kk=0;kk<a_tab->size;kk++) a_tab->table[kk] = -1;
459     for (kk=0;kk<oldsize;kk++) {
460       if (oldtable[kk] != -1) {
461         ierr = PCGAMGHashTableAdd(a_tab, oldtable[kk], olddata[kk]);CHKERRQ(ierr);
462        }
463     }
464     ierr = PetscFree(oldtable);CHKERRQ(ierr);
465     ierr = PetscFree(olddata);CHKERRQ(ierr);
466     ierr = PCGAMGHashTableAdd(a_tab, a_key, a_data);CHKERRQ(ierr);
467   }
468   PetscFunctionReturn(0);
469 }
470 
471